Certain derivatives of pyrazinylmalonates

ABSTRACT

The compounds are of the class of pyrazine, arylpyrazine, diphenylpyrazine, and cycloalkylpyrazine malonates, acetates, acetamides, and acetic acids, useful for their ultraviolet light absorption properties.

United States Patent [191 Schwartz et al.

[4 1 Aug. 26, 1975 CERTAIN DERIVATIVES OF PYRAZINYLMALONATES Inventors: Norman Schwartz, Philadelphia;

Richard J. Mohrbacher, Fort Washington, both of Pa.

Assignee: McNeil Laboratories, Incorporated,

Fort Washington, Pa.

Filed: Nov. 17, 1972 Appl. No.: 307,683

Related US. Application Data Division of Ser. No. 774,486, Nov. 8, 1968, Pat. No. 3,761,477.

US. Cl 260/250 B; 424/250; 260/45.8 N Int. Cl. C071) 241/02 Primary E.\'aminerNicholas S. Rizzo Attorney, Agent, or FirmSalvatore R. Conte [5 7] ABSTRACT The compounds are of the class of pyrazine, arylpyrazine, diphenylpyrazine, and cycloalkylpyrazine malonates, acetates, acetamides, and acetic acids, useful for their ultraviolet light absorption properties.

5 Claims, No Drawings CERTAIN DERIVATIVES OF PYRAZINYLMALONATES This is a divisional application of my copending application Ser. No. 794,486, filed Nov. 8, 1968, now issued as US. Pat. No. 3,761,477.

This invention relates to certain novel pyrazineacetic acids, acetates, and acetamides. More particularly, this invention is concerned with arylpyrazine and cycloalkylpyrazine malonates, acetates, acetamides,

and acetic acids having the formulae i1 N i TX R R wherein R is a member selected from the group consisting of phenyl, chlorophenyl, dichlorophenyl fluorophenyl, trifluoromethylphenyl, loweralkoxyphenyl, diloweralkoxyphenyl, loweralkylphenyl, diloweralkylphenyl, cyclohexyl and cyclopentyl; R is a member selected from the group consisting of hydrogen and loweralkyl; R is a member of the group consisting of hy' wherein R, is a member selected from the group consisting of hydrogen andloweralkyl; R is a member selected from the group consisting of hydrogen, loweralkyl, loweralkyl earboxylate ester, and sodium, calcium, and ammonium earboxylate salts; and Z is a member selected from the group consisting of loweralkyl carboxylate ester, carboxylic acid, and sodium, calcium, and ammonium earboxylate salts; wherein when R; is respectively loweralkyl earboxylate ester or earboxylate salt. Z is also respectively loweralkyl earboxylate ester or earboxylate salt.

This invention is further concerned with diphenyl pyrazine malonates, acetates, acetamidcs and acetic acids'having the formula:

,8 c H N c -x l (III) I wherein R is a member selected from the group consisting of hydrogen and loweralkyl; R is a member selected from the group consisting of hydrogen, loweralkyl, loweralkyl earboxylate ester, and sodium. calcium, and ammonium earboxylate salts; X is a member selected from the group consisting of loweralkyl earboxylate ester, carboxylic acid, carboxamide, a member selected from the group consisting of N-loweralkyl-, N,N-diloweralkyl, N-aryl-, N-aralkyl-, and N-heterocyclic-substituted carboxamides, and sodium, calcium, and ammonium carboxylate salts; and wherein when R is respectively loweralkyl earboxylate ester or earboxylate salt, X is also respectively loweralkyl earboxylate ester or earboxylate salt.

The term loweralkyl includes alkyl groups containing 1 to 7 carbon atoms, and preferably 1 to 4 carbon atoms, including saturated aliphatic chains, straight or branched, such as methyl, ethyl, propyl, isopropyl, nbutyl, and isobutyl.- I

The compounds of this invention absorb ultraviolet light and are useful as sunscreening materials in salves I and ointments. In addition, because of their solubility in organic materials generally, they may be used asultraviolet absorbers in plastics and resins, such as polystyrene, polyethylene, polypropylene, polyacrylics (methacrylate resins, polyaeylamides, polyacrylonitrile fibers), polyamide fibers (nylon e.g. and polyester fibers. In the latter use, the inclusion of ().()l to 5 percent of the absorber, based on the polymer weight, is sufficient to render protection against ultraviolet light, such as in plastic film or light filters. The absorber may be incorporated in the mixtures of monomers before polymerization to form the polymer or it may be incorporated in the polymer at any stage during its handling, as by milling into the polymer together with other compounding ingredients or during the spinning of polymers into fibers, etc.

Due to the asymmetric center present in the subject compounds wherein R and R are different, except where R; is identical with X or Z, it is evident that the existence of such compounds in the form of resolved enantiomorphs is possible. It is naturally intended that such enantiomorphs are included within the scope of this invention.

Compounds of Formula I and Formula ll, wherein R is hydrogen or loweralkyl, R is loweralkyl earboxylate,

and X and Z is loweralkyl earboxylate are prepared byreacting the appropriate 2-chloropyrazine derivative with diloweralkyl malonate or diloweralkyl loweralkylmalonate in the presence of sodium hydride in a suitable solvent such as dimethylformamide. As an alterna-' tive process, sodamide and liquid ammonia may be employed in place of sodium hydride and dimethylformamide. I

Compounds of Formula I and Formula ll wherein R and R are both hydrogen or R is hydrogen and R is loweralkyl and X or Z is loweralkyl earboxylate are prepared by heating the foregoing diloweralkyl pyrazinylmalonate and diloweralkyl a-loweralkylpyrazinylmalonate derivatives in a suitable solvent such as dimethyl sulfoxide in the presence of sodium cyanide.

Compounds of Formula I and Formula ll wherein R and R- are both hydrogen or R is hydrogen and R is loweralkyl and X or Z is carboxylic acid are prepared by refluxing the foregoing loweralkyl pyrazineacetate and loweralkyl a-loweralkylpyrazineacetate derivatives in aqueous sodium hydroxide and acidifying the resulting hydrolyzate. In an alternative procedure, the

pyrazineacetic acid derivatives may be prepared by treating the diloweralkyl pyrazinylmalonates and the diloweralkyl a-loweralkylpyrazinylmalonates of Formula l and Formula ll with a base such as aqueous soeacetates may be reacted with sodium hydride in di methylsulfoxide followed by reaction of the anion thus produced with a loweralkyl halide, preferably the iodide.

dium hydroxide, and thereafter acidifying the solution 5 The compounds of Formula I and II wherein R and Compounds of Formula I wherein X is carboxamid R are each loweralkyl and X or Z are loweralkyl carare prepared by reacting the aforesaid pyrazineacetate hoxylate may be converted to the corresponding acetand a-loweralkylpyrazineacetate riv i with amides and acetic acids by the procedures described moni m hydroxide. hereinbefore for the compounds wherein R is loweral- In an alternative procedure, loweralkyl esters of the ll) k d R i h d acetic acids of F rm l I and F rm l I may be pre- The N-substituted acetamides of this invention may pared from the corresponding acids by conventional h e ared b ti the orre di a eti a id esterificiltion Procedures In another alternativeprocederivatives of this invention with thionyl chloride and dure, the acetamides of Formula I may be reacted with then with the desired arnine aqueous hydrochloric acid avoiding excess p 5 The salts of the acetic acid derivatives of this inventures, or with sodium or ammonium hydroxide and i may b prepared b reacting th corresponding thereafter, acidifying t0 form the Corresponding acid in water with sodium, calcium, or ammonium hypyrazineacetic acid derivatives. droxide.

Compounds of Formula I and II wherein R and R Compounds of the Formula [II are prepared in the are each loweralkyl and X or Z are loweralkyl carboxsame manner as in the case of compounds of Formula ylate are prepared by reacting a loweralkyl halide, such I and Formula ll, using 5-chloro-2.3- ipheny py zine as methyl, ethyl, isopropyl or n-butyl iodide, with the as the starting material. aforementioned loweralkyl oz-loweralkylpyrazineace- Th following schematicdiagram, exemplifying the tates in the presence of sodamide in liquid ammonia. 7 preparation of Formula I type compounds, illustrates As an alternative, the lower-alkyl a-loweralkylpyrazinthe foregoing syntheses:

N CHCO a: N 2 U R R l R 1 diothyl loweralkyl DMSO mulonatc NCH R Y 1 +N H and DMF N l 2 E f or I sodumid. and liquid R ammonia N I co in C NaCN 2 2 DMSO (1) NoOH N (2)HCI NuOH;

than ucidif N NH N :1

HCO c 2 HC] CHCOOH or R R NcOH and acidif lhiar l chloride;

7. N I II N CHCONR R CHCOC] R NHR' R l loworalk l amines I V N hetero qmi n'os, N

or crulkyl amine; (mono--or di--substitution) The following schematic diagram illustrates the preparation of the starting materials used in the synthesis of 3U the novel compounds of this invention:

O H 2 i 2 i HCl R 0 H N N on N c1 NaOH P0613 i methano I pressure ethanol, or and heal R water R N N H N O 2 CONH 2 H o NuH$O3 O R H N o N CONH i docarboxylcte R N CH 1aoc.

The following examples are intended to illustrate, but not to limit. the scope of the present invention.

EXAMPLE I To a mixture of phenylglyoxal hydrate (41.5 g.. 0.27 mole) in 250 ml. of methanol at 40 (dry ice-carbon tetrachloride-acetone) is added, with stirring, glycinamide hydrochloride (30.0 g.. 0.27 mole) in 250 ml. of methanol. precooled to 40 C. To this stirred mixture 50 ml. of 12.5 N sodium hydroxide is added dropwise while the temperature is maintained at 30 C. The temperature is raised to between -20 and 10 for /2 hour, to for 2 hours, and finally to room temperature for 2 hours. The reaction mixture is then cooled in an ice-bath and treated dropwise with 45 ml. of concen' trated hydrochloric acid. The pH of the mixture is adjusted to 5 by the portionwise addition of 27 g. of sodium bicarbonate. The mixture is filtered. The solid material is recrystallized from n-butanol. The product is 5-phenylpyrazinol; m.p. 208-2l0 C.

EXAMPLE ll p-Chlorophenylglyoxal hydrate is prepared in two steps of abromo-p-chloroacetophenone as described by Kornblum and Frazier 1]. Am. Chem. Soc., 88 865 (1966)]. To the p-chlorophenylglyoxal hydrate (26.5 g.. 0.14 mole) in 130 ml. of methanol cooled to 30 is added. with stirring, glycinamide hydrochloride (15.7 g.. 0. 14 mole) in 130 ml. of methanol precooled to 30 C. To the stirring mixture is added dropwise 26 ml. of 12.5 N sodium hydroxide while the temperature is raised and is maintained at 5 to 0 C. for 2 hours. The mixture is then stirred at ambient temperature for 2% hours. Concentrated hydrochloric acid (24 ml.) is added dropwise to the mixture with ice-bath cooling. This is followed by the portionwise addition of sodium bicarbonate 15 g.). The reaction mixture is refrigerated overnight,'filtered and the solid is washed with water and recrystallized from'95 percent ethanol. The product is 5-(p-chlorophenyl)pyrazinol; mp. 21 822 1 C.

EXAMPLE lll To phosphorous oxychloride (70 ml.) containing sulfuric acid (4 drops) in a pressure bottle is added 5- phenylpyrazinol (18.3 g.. 0.106 mole), with swirling. The open bottle is heated at 125 C. for V2 hour to allow the evolution of hydrogen chloride. The bottle is closed and the mixture is heated at 125 C. for 5 hours. The bottle is cooled and the reaction solution is poured onto a stirred mixture of 70 0 g. of ice and 300 ml. of chloroform. After about minutes. the mixture is cooled in an ice-salt bath and slowly neutralized with concentrated ammonium hydroxide. followed by the addition of 50 percent sodium hydroxide to make the mixture basic. The mixture is filtered through celite, the layers are separated. and the aqueous layer is extracted twice more with chloroform. The combined chloroform extracts are dried (Na sO and evaporated. The solid material is recrystallized from methanol. The product obtained is 2-ch1oro-5- phenylpyrazine'. m.p. 96 98 C.

EXAMPLE IV A sodium hydride-mineral oil suspension (54 percent, 28 g., 0.62 mole) is stirred with three 150 ml. portions of dry hexane (Na SO each portion being pipetted out to remove the mineral oil. Dimethylformamide (previously distilled and dried over a molecular sieve; 180 ml.) is added through a pressure equalized additional funnel while a slow stream of nitrogen is passed through the mixture. The reaction vessel is cooled in an ice-bath and diethyl methylmalonate (99.5 g.. 0.57 mole) is added dropwise to the stirred mixture. After addition is complete, the ice-bath is replaced by an oil bath and the temperature is raised to 50 C. A solution of chloropyrazine (50 g.. 0.44 mole) in dimethylformamide (50 ml.) is added dropwise. The mixture is then heated for 3 hours, raising the temperature during this period to 120 C. I

The reaction mixture is cooled to about C. and water (20 ml.) is added. The mixture is concentrated to a small volume and the residual liquid is diluted with ice-water (300 m1.) and extracted several times with ether. The combined ether extracts are washed with 5 percent hydrochloric acid. then with water. dried, and evaporated. The resulting liquid is distilled. The product obtained is diethyl a-methylpyrazinylmalonate; b.p, ll41 18 C. 0.5 mm.)

EXAMPLE V A sodium hydride-mineral oil suspension (547:; 3.1 g.. 0.069 mole) is stirred with three 50 ml. portions of dry hexane, each portion being pipetted out to remove the mineral oil. Dimethylformamide (30 ml.. previously distilled and dried over a molecular sieve) is added through a pressure equalized addition funnel while a slow stream of nitrogen is passed through the mixture. The reaction vessel is cooled in an ice-bath while diethyl methylmalonate (12 g., 0.069 mole) is added dropwise to the stirred mixture. After the addition is complete, the ice-bath is replaced by an oil bath and the temperature is raised to 50 C. To the mixture is added dropwise 2-chloro-5-phenylpyrazine (10 g.. 0.053 mole) in warm dimethylformamide (55 ml.). After this addition is complete, the mixture is heated for 3 hours during which time the temperature is raised to 120 C. The reaction mixture is cooled to about C. and water (4 ml.) is added. The mixture is concentrated to a small volume. and the residual liq-. uid is diluted with 50 g. of ice and extractedwith ether several times. The combined ether extractsare washed with 5 perc'ent hydrochloric acid, then with water..and then dried and evaporated. The resulting oil is chromatographed on a column of 500 g. of Merck acidwashed' alumina. Elution with benzene-hexane (4:1) through ethyl acetate-benzene (1:3) yielded diethyl a-methyl-S-phenylpyrazinylmalonate.

A mixture of diethyl a-methyl-S-phenylpyrazinylmalonate (10.3 g.. 0.031 mole) and sodium cyanide (3.2 g.. 0.065 mole in dimethyl sulfoxide ml.) is stirred and heated at C. for A hour. The reaction mixture is poured onto 300 g. of ice saturated with so dium chloride. and extracted several times with ether. The combined other extracts are washed with water. dried. and evaporated. The resulting material is triturated with warm hexane and filtered. The hexane filtrate is evaporated and the resulting oil is distilled. The third fraction. which solidifies. is recrystallized from pentane and filtered at dry ice temperature. The prod- 1'1 uct obtained is ethyl a-methyl-5-phenylpyrazineacetate; m.p. 3840 C.

EXAMPLE VII A mixture of diethyl oz-methylpyrazinylmalonate. g., 0.08 mole) and sodium cyanide (8 g.. 0.16 mole) in dimethyl sulfoxide (150 ml.) is stirred and heated between ll60 C. for 1 hour. The reaction mixture is poured into 400 ml. of ice water saturated with sodium chloride. and the mixture is extracted several times with ether. The ether extracts are combined and washed with water until neutral. dried. and evaporated. The resulting liquid is distilled. The product obtained is ethyl a-methylpyrazineacetate; b.p. 71-73 C. (0.4 mm.). 7 7

EXAMPLE VIII A mixture of diethyl ez-methylpyrazinylmalonate (20 g.. 0.08 mole). in 50 percent sodium hydroxide ml.) is stirred and refluxed for 1% hours. The solution is cooled to room temperature, washed with ether. acidified. saturated with sodium chloride. and extracted several times with ether. The combined ether extracts are dried and evaporated. The solid material is recrystallized by dissolving in warm benzene (with temperature below C.) and then concentrating the solution under a stream of nitrogen with temperature below 50 C. The resulting mixture is filtered. The product obtained is a-methylpyrazineacetic acid; m.p. 9596 C. dec.

EXAMPLE IX A mixture of ethyl oz-methyl-5-phenylpyrazineacetate (1.0 g.. 0.0039 mole). water (8 ml.), and 50 percent aqueous sodium hydroxide (2 ml.) is refluxed for hour. The reaction solution is cooled to room temperature and diluted with water. The solution is washed three times with ether. chilled in an ice-bath. rendered acidic with concentrated hydrochloric acid. and filtered. The solid material is recrystallized from benzene-hexane (temperature kept below 60 C.). The product obtained is a-methyl-S-phenylpyrazineacetic acid; m.p. l05l07 C. dec.

EXAMPLE X Concentrated ammonium hydroxide (80 ml.) added to ethyl a-methylpyrazineacetate (8.0 g.. 0.044 mole) at ice-bath temperature. The mixture is stirred at room temperature for 2 hours. and then is saturated with sodium chloride and extracted with chloroform several times. The combined chloroform extracts are dried and evaporated. The solid material is recrystallized from ethyl acetate. The product obtained is a-methylpyrazineacetamide; m.p. 9698 C. 5

EXAMPLE XI A mixture of ethyl a-methyl-5-phenylpyrazineacetate (5.0 g. 0.02 mole) and concentrated ammonium hydroxide 100 ml.)'is stirred at room temperature for 3 days in a stoppered flask. The reaction mixture is chilled and filtered. The solid material is recrystallized from benzene. The product obtained is a-methyl-S- phenylpyrazineacetamide; m.p. l52l 54.

EXAMPLE XII A 12 g. (0.058 mole) sample of 5-(p-chlorophenyl)- pyrazinol is added to phosphorous oxychloride (40 ml.)

i2 containing suiluric acid (3 drops) in a pressure bottle. The mixture is swirled briefly and heated in the open bottle at 120 C. for /z hour to allow the evolution of hydrogen chloride. The bottle is closed and heated at about 125 C. for 4 hours. The bottle is cooled and the contents are poured onto a stirred mixture of 370 ml. of icewater and 200 ml. of chloroform. The mixture is chilled and slowly neutralized with concentrated ammonium hydroxide; a sufficient quantity of 50 percent sodium hydroxide is added to render the mixture basic. The mixture is filtered through celite. the layers separated. and the aqueous layer is extracted twice more with chloroform. The combined chloroform extracts are dried and evaporated. The solid material is recrystallized from methanol. The product obtained is 2- chloro-5-(p-chlorophenyl)pyrazine; m.p. l45146 C.

EXAMPLE XIII A sodium hydride-mineral oil suspension (54 percent; 1.8 g.. 0.04 mole) is stirred with three 25 ml. portions of dry hexane. each portion being pipetted out to remove the mineral oil. Dimethylformamide (30 ml.. previously distilled and dried over a molecular sieve) is added through a pressure equalized addition funnel while a slow stream of nitrogen is passed through the mixture. The reaction vessel is cooled in an ice-bath and diethyl methylmalonate (7 g..' 0.04 mole) is added dropwise to the stirred mixture. After the addition is complete, the ice-bath is replaced by an oil bath and the temperature is raised to 50 C. A solution of 2- chloro-5-(p-chlorophenyl )pyrazine (8 g.. 0.0355 mole) in warm dimethylformamide ml.) is added dropwise. After this addition is complete, the mixture is heated for 3 hours during which time the temperature is raised to 120 C.

The reaction mixture is cooled to C. and water (3 ml.) in added. The mixture is concentrated to a small volume. The residual liquid is diluted with 40 m1. of icewater and extracted with ether several times. The combined ether extracts are washed with 5 percent hydrochloric acid. then with water. dried. and evaporated The solid material is recrystallized from hexane. The product obtained is diethyl 5-(p-chlorophenyl)-amethylpyrazinylmalonate; m.p. 6264 C.

EXAMPLE XIV A mixture of diethyl 5-(p-chlorophenyl)-amethyl pyrazinylmalonate (7.0 g. 0.019 mole) and sodium cyanide (2.0 g.. 0.04 mole) in dimethyl sulfoxide (60 ml.) is stirred and heated at C. for /2 hour. The reaction mixture is poured into 200 ml. of ice-water saturated with sodium chloride. The material is extracted several times with ether. The combined ether extracts are washed with water. dried. and evaporated. The crude product is chromatographed on a column of acid washed alumina. Elution with benzene-hexane (1:4 through'4zl followed by benzene is undertaken. The solid material is recrystallized twice from pentane. The product obtained is ethyl 5-(p-chlorophenyl)-amethylpyrazineacetate; m.p. 4749 C.

EXAMPLE XV A mixture ofethyl 5-(p-chlorophenyl )-(.t-methylpyrazincacetatc (2.33 g.. 0.0080 mole). water (24 ml. and 50 percent aqueous sodium hydroxide (6 ml.) is refluxed for 1% hours. The reaction mixture is diluted with about 30 ml. of water. washed three times with ether. chilled in an ice-bath. and thenacidified with concentrated hydrochloric acid. The solid material is filtered and recrystallized from benzene-hexane (temperature kept below 50 C.). The product obtained is S-(p-chlorophenyl)-a-methylpyrazineacetic acid; m.p. ll1l 12 C. dec.

EXAMPLE XVI A mixture of ethyl p-chlorophenyl )-oz-methylpyra zineacetate (0.90 g. 0.0031 mole) and concentrated ammonium hydroxide (50 ml.) is stirred in a stopperecl flask for 3 days at room temperature. Thereaction mixture is chilled and filtered. The solid material is recrystallized from benzene. The product obtained is 5-(pchlorophenyl )-a-methylpyrazineacetamide;

EXAMPLE XVll mixture is poured into dilute hydrochloric acid. The

ether layer is separated and washed successively with sodium hisulfite solution. sodium bicarbonate solution.

and water. The ether solution is dried and evaporated. The solid material is recrystallized from pentane. The product obtained is ethyl a.a-dimethyl-5phenylpyrazineacetate.

EXAMPLE XVIII Using the procedure of Example XI and replacing ethyl oz-methyl-S-phenylpyrazineacetate with an equivalent amount of ethyl aa-dimethyl-S-phenylpyrazineacetate. the product obtained is a.a-din1ethyl-5- phenylpyrazineacetamide.

EXAMPLE XIX Using the procedure of Example [X and replacing ethyl oz-methyl-5-phenylpyrazineacetate with an equivalent amount of ethyl apt-dimethyl-5-phenylpyrazineacetate. the product obtained is ma-dimethyl-S-phenyl-pyrazineacetic acid.

EXAMPLE XX uct obtained benzylacetamide.

EXAMPLE XXl V A mixture of oz-rnethyl-5phenylpyrazineacetic acid (3.0 g., 0.013 mole) and thionyl chloride (30 ml.) is stirred and warmed at about 60 for hour. The reaction solution is cooled in an ice-bath. A solution of morpholine (1.2 g., 0.014 mole) in benzene m1.) is added. The mixture is warmed on the steam bath for hour, cooled, and diluted with water. The aqueous mixture is extracted severaltimes with ether. The combined ether extracts are washed with dilute hydrochloric acid, dilute sodium bicarbonate, and water, and then dried and evaporated. The solid residue is recrystallized from benzene. The product obtained is 4-(a-methy1-5-phenylpyrazineacety1)morpholine.

EXAMPLE XXII 3 Hydroxy-5-phenylpyrazine-2-carboxamide is prepared by the method of Dick, Wood and Logan, .1. Chem. Soc., 2131 (1956). The carboxamide is converted'to 6phenylpyrazinol by the method of Jezo and Luzak. Chem. Zvest., 22, 190 1968), using percent sulfuric acid at C. Using the procedure of Example 111 and replacing S-phenylpyrazinol with an equivalent amount of o-phenylpyrazinol, the product obtained is 2-chloro-orphenylpyrazine. Using the procedure of Example V and replacing 2-chloro-5- phenylpyrazine with an equivalent amount of 2-chloroo-phenylpyrazine, the product obtained is diethyl 01 methyl-o-phenylpyrazinylmalonate; Using the procedure of Example V1 and replacing diethyl a-methyl-S- phenylpyrazinylmalonate with an equivalent amount of diethyl a-methyl-o-phenylpyrazinylmalonate the product obtained is ethyl a-methyl-6-phenylpyrazineacetate. Using the procedure of Example IX and replacing ethyl a-methyI-S-phenylpyrazineacetate with an equivalent amount of ethyl a-methyl-6-phenylpyrazineacetate, the product obtained is a-methyl-ophenylpyrazineacetic acid. Using the procedure of Example X1 and replacing ethyl a-methyl-S -phenylpyrazineacetate with an equivalent amount of ethyl oz-methyl-o-phenylpyrazineacetate, the product obtained is p-Chlorophenylglyoxal hydrate is treated with an aqueous sodium bisulfite solution. The mixture is then heated with an equimolar portion of aminomalonamide dissolved in water. The product obtained is 3-hydroxy- 5-(p-chlorophenyl)pyrazine-2-carboxamide. The carboxamide is heated at 180 C. in 80 percent sulfuric acid. The product obtained is 6-(pchlorophenyl)pyrazinol. Using the procedure of Example 111 and replacing S-phenylpyrazinol with an equivalent amount of 6-( p-chlorophenyl )-pyrazinol. the product obtained is 2-chloro-6-(p-chlorophenyl)pyrazine. Using the procedure of Example V and replacing 2-chloro-5-phenylpyrazine with an equivalent amount of 2-chloro-6(p-chlorophenyl)pyrazine. the product obtained is diethyl oz-methyl-6-(p-chlorophenyl)- pyrazinylmalonate. Using the procedure of Example V1 and replacing diethyl amethyl- S-phenylpyrazinylmalonate with an equivalent amount of diethyl a-methyl- 6-( p-chlorophenyl )pyrazinylmalonate the productobtained is ethyl oz-methyl-6-(p-chlorophenyl)pyrazineacetatc. Using the procedure of Example 1X and replacing ethyl a-methyl-5-phenylpyrazineacetate with an equivalent amount of ethyl a-methyl-o-(pchlorophenyl)-pyrazineacetate, the product obtained is a-methyl-6(p-chlorophenyl )pyrazineacetic acid.

Using the procedure of Example XI and replacing ethyl a-methyl-S-phenylpyrazineacetate with an equivalent amount of ethyl oz-methyl-6-(pchlorophenyl)pyrazineacetate, the product obtained a-methyl-o-(pchlorophenyl)pyrazineacetamide.

EXAMPLE XXIV ample XI and replacing ethyl oz-methyl-S-phenylpyrazineacetate with an equivalent amount of ethyl oz-methyl3-phenylpyrazineacetate, the product obtained is a-methyl-3-phenylpyrazineacetamide.

EXAMPLE XXV 2-Chloro-3-(p-chlorophenyl)pyrazine is prepared by the method of Karmas and Spoerri (loc. cit.), using 3- (p-chlorophenyl)pyrazinol as the starting material. Starting with this material and using the procedures of Examples V, VI, IX, and XI, the products obtained are diethyl a-methyl-3-(p-chlorophenyl)pyrazinylmalonate, ethyl a-methyl-3-(p-chlorophenyl)pyrazineacetate, a-methyl-3-(p-chlorophenyl)pyrazineacetic acid, and a-methyl-3-(p-chlorophenyl )pyrazineacetamide.

EXAMPLE XXVI a-Bromocyclohexane acetyl bromide is prepared by the Hell-Volhard-Zelinsky reaction (Hell, Ber., 14, 891, I881; Zelinsky, Ben, 20, 2026,1887; Volhard. Ann., 242, I4], 1887) starting with cyclohexylacetic acid. The a'bromocyclohexane acetyl bromide is reacted with ammonia to produce a-aminocyclohexylacetamide. Equimolecular portions of percent aqueous glyoxal and oz-aminocyclohexylacetarnide are dissolved in aqueous methanol, and the mixture is treated with sodium hydroxide in the cold. The product obtained is 3-cyclohexylpyrazinol. Starting with this product and using the procedures of Examples III, V, VI, IX, and XI, the products obtained are 2-chloro-3- cyclohexylpyrazine, diethyl a-methyI-3-cyclohexylpyrazinylmalonate, ethyl oz-methyl3-cyclohexylpyrazineacetate. a-methyl-3-cyclohexylpyrazineacetic acid, and oz-methyl-3-cyclohexylpyrazineacetamide.

EXAMPLE XXVII Using the procedure of Example XXIII and replacing p-chlorophenylglyoxal hydrate with an equivalent amount of cyclohexylglyoxal hemihydrate, the product obtained is 3-hydroxy-5-cyclohexylpyra2ine-2- carboxamide. The carboxamide is heated at 180 C. in 80 percent sulfuric acid. The product obtained is 6- cyclohexylpyrazinol. Starting with this material andv using the procedures of Examples III, V, VI, IX. and XI, the products obtained are 2-chloro-6- cyclohexylpyrazine, diethyl a-methyl-o-cyclohexylpyrazinylmalonate, ethyl a-methyl-6cyclohexylpyrazineacetate, a-methyl-o-cyclohexylpyrazineacetic acid, and oz-methyl-6-cyclohexylpyrazineacetamide.

EXAMPLE XXVIII Using the procedure of Example I and replacing phe nylglyoxal hydrate with an equivalent amount of cyclohexylglyoxal hemihydrate, the product obtained is 5-cyclohexlpyrazinol. Starting with this material and using the procedures of Examples III, V, VI, IX, and XI, the products obtained are 2-chloro-5- cyclohexylpyrazine, diethyl a-methyl-S-cyclohexylpyrazinylmalonate, ethyl a-methyl-S-cyclohexylpyrazineacetate, a-methyl-5-cyclohexylpyrazineacetic acid, and oc-methyl-S-cyclohexylpyrazineacetamide.

EXAMPLE XXIX Using the procedure of Kornblum and Frazier, 1. Am. Chem. Soc., 88, 865 (I966), substituted phenylglyoxals, such as p-methylphenylglyoxal, p-methoxyphenylglyoxal, m-chlorophenylglyoxal, ochlorophenylglyoxal, p-fluorophenylglyoxal, 2,5- dichlorophenylglyoxal, p-trifluoromethylphenylglyoxal, 2,3-dimethylphenylglyoxal, and 2,3-dimethoxyphenylglyoxal, are prepared from the corresponding substituted acetophenones. The substituted phenylglyoxals are used in the preparation of the corresponding S-(substituted-phenyl)pyrazinols by the procedure of Example II. The 2-chloro-5-( substitutedphenyl )pyrazines are prepared by the method of Example XII. The diethyl a-methyl-5-(substituted-phenyl)- pyrazinylmalonates are prepared by the method of Example XIII. The ethyl a-methyl-5-(substituted-phenyl)- pyrazineacetates are prepared by the method of Exam ple XIV. The a-methyl-S-(substitutedphenyl)pyrazineacetic acids are prepared by the method of Example XV. The a-methyl-5-(substitutedphenyl)pyrazineacetamides are method of Example XVI.

EXAMPLE XXX Using the procedure of Example XXIII and replacing p-chlorophenylglyoxal with substituted phenylglyoxals such as those identified in Example XXIX, the corresponding o-(substituted-phenyl)pyrazinols are obtained. Correspondingly by the procedures of Examples XII, XIII, XIV, XV, and XVI, the corresponding 2-chloro-6-(substituted-phenyl)pyrazines, diethyl a-methyl-6-(substituted-phenyl)pyrazinylmalonates, ethyl-a-methyl-6-( substituted-phenyl )pyrazineacetates, a-methyl-6( substituted-phenyl )pyrazineacetic acids, and a-methyl-6(substitutedphenyl)pyrazineacetamides are obtained.

EXAMPLE XXXI Using the procedure of Karmas and Spoerri (J. Am. Chem. Soc., 78, 4071, 1956), and starting with pyrazino] and substituted phenyldiazonium chlorides, such as p-methylphenyldiazonium chloride, p-mcthoxyphenyldiazonium chloride. m-chlorophenyldiazonium chloride, o-chlorophenyldiazonium chloride. pfluorophenyldiazonium chloride, 2,5- dichlorophenyldiazonium chloride, p-trifluoromethyl phenyldiazonium chloride, 2,3-dimethylphenylprepared by the diazonium chloride. and 2.3-dimethoxyphenyldiazonium chloride, the corresponding 3-(substitutedphenyl)pyrazinols are prepared. Starting with these materials and using the procedures of Examples XII, XIII, XIV, XV, and XVI, the products obtained are the corresponding 2-chloro-3-(substitutedphenyl)pyrazines, diethyl amethy'l-3-(substitutedphenyl )pyrazinylmalonates, ethyl a-methyl-3- (substituted-phenyl )pyrazineacetates, a-methyl-3- (substituted-phenyl)pyrazineacetic acids, and a-methyl-3-( substituted-phenyl )pyrazineacetamides.

EXAMPLE XXXII Using the procedure of Example XXI and replacing morpholine with an equivalent amount respectively of methylamine, dimethylamine, ethylamine, diethylamine, isopropylamine. and n-butylamine, the corresponding N-methyl-, N,N-dimethyl-, N-ethyl-, N,N- diethyl-, Nisopropyland N-n-butyl-acetamides are obtained. Repeating this procedure and replacing a-methyl-S-phenylpyrazineacetic acid with equivalent amounts of a-methyl-6-phenylpyrazineacetie acid and ct-methyl-3-phenylpyrazineacetic acid, the corresponding N-substituted amides of these compounds are obtained.

EXAMPLE XXXIII and XI, the products obtained are the corresponding pyrazineacetic acids, and

ethyl pyrazine-acetates, pyrazineacetamides.

EXAMPLE XXIV Using the procedure of Example IV, replacing diethyl methylmalonate with an equivalent amount of diethyl malonate, the product obtained is diethyl pyrazinylmalonate. Starting with this material and using the procedures of Examples VI and IX the products obtained are ethyl pyrazineacetate and pyrazineacetic acid.

EXAMPLE XXXV Using the procedure of Example XVII and replacing methyl iodide with equivalent amounts of ethyl iodide. isopropyl. iodide, and n-butyl iodide. the products obtained are ethyl u mcth \'l-zt-ethyl-5phenylpyrazineacctate, ethyl a-methy]-a-isopropyl-S-phenylpyrazineacetatc. and ethyl zz-methyl-u-( n-butyl )-5- phcnylpyrazincactate. I

EXAMPLE XXXVI Using the procedure of Example IX and replacing ethyl a-methyl-S-phenylpyrazineacetate with equivalent amounts of the products of Example XXXV, the products obtained are a-methyl-a-ethyl-S- phenylpyrazineacetic acid, a-methyl-oc-isopropyl-S- phenylpyrazineacetic acid and a-methyl-oz-(n-butyU-S- phenylpyrazineacetic acid.

EXAMPLE XXXVII Using the procedure of Example XI and replacing ethyl oz-methyl-S-phenylpyrazineacetate with equivalent amounts of the products of Example XXXV, the products obtained are a-methyl-a-ethyl-5- phenylpyrazineacetamide, a-methyl-a-isopropyl-S- phenylpyrazineacetamide, and a-methyl-a-( n-butyl )-5- phenylpyrazineacetamide.

EXAMPLE XXXVII] Using the procedure of Example V, employing 2- chloro-R-pyrazines having the formula wherein R has the same values as in Formula I hereinabove, and replacing diethyl methylmalonate with equivalent amounts of diethyl ethylmalonate, diethyl isopropylmalonate, and diethyl n-butylmalonate, the products obtained are diethyl a-substituted-R- pyrazinylmalonates having the formula wherein R has the same value as above and a is respectively ethyl, isopropyl, and n-butyl. Starting with these products and using the procedure of Example VI, the products obtained are the corresponding ethyl a-substituted-R-pyrazineacetates. Starting with these products and using the procedures of Examples IX and XI, the corresponding acetic acids and acetamides are obtained.

EXAMPLE XXxix Using the procedure of Example XVII, employing the ethyl a-substituted-R-pyrazineacetates of Example XXXVIII, and replacing methyl iodide with equivalent amounts of ethyl iodide, isopropyl iodide, and n-butyl iodide, the products obtained are the ethyl 0c, oi -disubstituted-R-pyrazineaeetates having the structural formula C'COCH wherein R has the same value as in Formula 1 hereinabove and wherein a and 04 are the following:

pyrazineacetic acids are prepared by the method of Example lX. The corresponding uhoF-disu'bstituted-R- pyrazineacetamides are prepared by the method of Example XI.

EXAMPLE XL Sodium hydride (54 percent in mineral oil; 6.l g. 0.14 mole) is stirred with three portions (60 ml.) of dry hexane. each portion being pipetted out to remove the mineral oil. Dimethylformamide (previously distilled and dried over a molecular sieve; 55 ml.) is added through a pressure-equalized addition funnel while a slow stream of nitrogen is passed through the mixture.

The reaction vessel is placed in an ice-bath and diethyl methylmalonate (24 g., 0.14 mole) is added dropwise to the stirred mixture. After the addition is complete. the ice-bath is replaced by an oil bath and the temperature is raised to 50 C. A solution of -chloro-2 3- diphenylpyrazine (28 g.. 0.1 1 mole) in warm dimethylformamide (1 ml.) is added dropwise. The mixture is heated for 3 /2 hours while the temperature is raised to 120 C.

The reaction mixture is cooled to about 80 C. and water (8 ml.) is added. The mixture is concentrated to a small volume. and the residual liquid is mixed with 800 g. of ice and extracted several times with ether. The combined ether extracts are washed with 5 percent hydrochloric acid, then with water, dried, and evaporated. The resulting oil is chromatographed on a column of acid-washed alumina. Elution with benzenehexane (3:2 thru 100 percent benzene) is undertaken. The product obtained is diethyl a-methyl-Sb-diphenylpyrazinylmalonate.

EXAMPLE XLI A mixture of diethyl oz-methyl-S,o-diphenyl pyrazinylmalonate. (4.5 g. 0.01 1 mole) and sodium cyanide (l.l g. 0.023 mole) in dimethyl sulfoxide (40 ml.) is stirred and heated between l40l65 C. for 1 hour. The reaction mixture is poured onto l00 g. of ice. saturated with sodium chloride. and extracted several times with ether. The combined ether extracts are washed with water, dried. and evaporateddThe resulting oil is purified by elution on a column of acid washed alumina with benzene-hexane (4:l thru 100 percent benzene). The product obtained is ethyl a-methyI- Sbdiphenylpyrazineacetatc.

EXAMPLE XLll Concentrated ammonium hydroxide (250 ml.) is added to a solution of ethyl oz-methyl-5,(w-diphenylpyra- Zineacetate (9.0 g.. 0.027 mole) in absolute ethanol (250 ml.). and the mixture is stirred in a stoppered flask for 5 days. The mixture is kept at room temperature with occasional warming to 50 C. Additional concentrated ammonium hydroxide 100 ml.) is added to the stirring mixture on the fourth day. The stopper is remove- .l'be mixture is diluted with another l00 ml. of concentrated ammonium hydroxide, and then warmed at 50 C. tori 5 minutes. The mixture is chilled and filte red. The ammoniacal ethanol filtrate is diluted with a largevolume of water. Sodium chloride is added, and the mixture is extracted several times with chloroform. The chloroform solution is dried and evaporated. The solid material is chromatographed on a column of 225 g. of acid washed alumina. Subsequent fractions are eluted with ethyl acetate and with ethyl acetatemethanol (9/1). The purest fraction is recrystallized from ethanol-water. The product obtained is a-methyl- 5.6-diphenylpyrazineacetamide; m.p. l23l25 C.

EXAMPLE XLIII A mixture of ethyl oz-methyl-S.o-diphenylpyrazineacetate (1.4 ,g.. 0.004 mole). ethanol (20 ml.), water (3 ml.) and 50% sodium hydroxide (3 ml.) is refluxed for 4 hours. The ethanol is evaporated and the aqueous residue is diluted with water and washed several times with ether. The aqueous layer is acidified in the cold with concentrated hydrochloric acid. The product is filtered and purified by careful recrystallization from ether-hexane or by dissolving in aqueous base and reforming with concentrated acid. The product obtained is oz-methyl-S.6diphenylpyrazineacetic acid; m.p. l27l28 C. dec.

EXAMPLE XLlV A mixture of diethyl a-methyl-5-phenylpyrazinylmalonate (4 g.. 0.0l2 mole) in water (32 ml.) containing 50% sodium hydroxide (8 ml.) is stirred and refluxed for 1% hours. The solution is evaporated to about half the original volume and chilled. The crystals formed are the disodium salt of a-methyl-S-phenylpyrazinylmalonic acid. Repeating the process but acidifying the solution after refluxing, and then adding sodium hydroxide, evaporating to half the original volume and chilling. the sodium salt of a-methyl-S- phenylpyrazineacetic acid is recovered. These proce dures are repeated using ammonium hydroxide and calcium hydroxide respectively and adjusting the reflux time to obtain the corresponding ammonium and calcium salts of a-methyl-S-phenylpyrazinylmalonic acid and a-methyl-5-phenylpyrazineacetic acid. In a similar manner, the salts of the other malonic acids and acetic acids of this invention are prepared.

EXAMPLE XLV A quantity of a-methyl-S.6-diphenylpyrazineacetic acid is heated at about C. for l5 minutes. The resulting melt is diluted with water and extracted several times with ether. The ether solution is dried and evaporated. The solid material is recrystallized from 95 percent ethanol. The product obtained is 2,3-diphenyl-5- ethylpyrazine; m.p. l02l04 C.

EXAMPLE XLVl Using the procedures of Example XXVI and thereafter Examples lll. V. VI. IX. and XI as shown in Example XXVI. and replacing cyclohexylacetic acid with an equivalent amount of cyclopentylacetic acid. the products obtained are 3-cyclopentylpyrazinol, 2-chloro-3- cyclopentylpyrazine, diethyl a-methyl-3-cyclopentylpyrazinylmalonatc ethyl a-methyl-3-cyclopentylpyi'azineacetate, a-methyl-3-cyelopentylpyrazineacetic acid. and a-methyl-3-cyclopentylpyrazineacetamide.

EXAMPLE XLVll EXAMPLE XLVlll Using the procedure of Example XXVlll and thereafter Examples Ill. V. VI. IX. and XI as shown inExample XXVlll. and replacing cyclohexylglyoxal with an equivalent amount of cyclopentylglyoxal, the products obtained are -cyclopentylpyrazinol. 2-chloro-5 cyclopentylpyrazine. diethyl a-methyl-S-cyclopentylpyrazinylmalonate. ethyl amethyl-5-cyclopentylpyrazineacetate. wmethyl-S-cyclopentylpyrazineacetic acid. and oz-methyLS-cyclopeiitylpyrazineacetamide.

EXAMPLE XLlX A mixture of diethyl oz-ethyl-S-phenylpyrazinylmalonate 18 g.. 0.053 mole). ml. of 50 percent sodium hydroxide, and 160 ml. of water is refluxed for 2 hours. The mixture is then diluted with water, washed several times with ether. and acidified with cold concentrated hydrochloric acidv The solid material is recovered by filtration and crystallized from benzene-hexane below 50 C. The product is oz-ethyl-S-phenylpyrazineacetic acid; m.p. 909l C. dec.

EXAMPLE L Using the procedure of Example XL. replacing diethyl methylmalonate with an equivalent amount of dicthyl ethylmalonate. the product obtained is diethyl a-ethyl-S.o-diphenylpyrazinylmalonate. Starting with this product and using the procedures of Examples XLl. XLlll, and XLII. the corresponding acetate, acetic acid. and acetamide are obtained.

TABLE I-Continued Amax. Example No. (MM

290 12.300 x111 255 18.600 1 287 19.200 305 13.900 xiv 254 16.900

305* 1 1.800 xv 254 18.000 2 18 16.100 300* 13 .000 XV[ 254 17.600 288 I 16.300 300* 13.200 XL 222 26.500 270* 11.700 283 12.100 310* 10.100 XLI 220 22.800 267 11.000 293 1 1.000 308* 10.000 XLii 220 23.400 265 11.500 292 11.300 310* 9.850 XLV 219 20.200 263 10.400 295 10.100 310* 8.850 X111 219 21.400

266 10.400 294 10.700 310* 9.300 XLlX 250 14.900 290 12.000

*shutildcr Certain of the novel compounds of this invention have been found to possess pharmacological activity as anti-inflammatory agents. These are identified by Example number in Table II. The test used is known as the kaolin-induced paw edema test. This test measures the ability of a compound. when administered in a single oral dose, to inhibit the swelling of the rat paw injected with a standard amount (0.1 ml.) of 10 percent kaolin suspension in saline. For comparative purposes. the activity of the compound to be tested is measured against TABLE I that produced by the known anti-inflammatory agent. phenylbutazoneln this assay, the test compound (0.4 Aniax. percent suspension or 0.4 percent solution. depending Emmpl on the compound) and phenylbutazone (0.4 percent w 363 solution) are administered in saline. Male Holtzman 5 rats are used in the assay. The results are recorded in 3 (0 2? Hi terms of percent inhibition produced by the compound 288 14.500 and by phenylbutazonev The percent inhibition is cal culated from the milliliters of mercury displaced as the 1 I 71,00 edema develops in the paw. The paw is placed in a pool of mercur immediatel after in'ection with the kaolin NH 790 gg y y J V1 267 (L700 suspension. and a reading '15 taken on the quantity of 272* 6.100 mercury displaced. The animal is then returned to the I W cage, allowing the edema to develop. After 6 hours. the

113W paw is again immersed in mercury and the quantity of X 2 7. mercury displaced is again measured. The method is 1 2 1 858' 60 described in J. Pharm. and Experimental 1 herapeutics. x1 249 15.400 162. l962()l (1968).

TABLE II No. Dosc (oral) Mg/Kg Inhibition /1 Example Rats Example PllLl'l \ll7Ulil2Ul1L' Example Plieiiylbutazonc dilowerulkoxyphenyl, loweralkylphenyl, diloweralkylphenyl. cyclohexyl and cyclopentyl; R, is a member selected from the group consisting of hydrogen and loweralkyl; R: is a member selected from the group consisting oflowernlkyl curboxylate ester, and sodium, calcium and ammonium carboxylate salts; and X is a member selected from the group consisting of loweralkyl carhoxylate ester, and sodium, calcium and ammonium carboxylate salts;

2. Diethyl a-methyl-S-phenylpyrazinylmalonzlte.

3. Diethyl a-ethyl-S-phenylpyrazinylmulonate.

4. Diethyl S-(p-chlorophenyl)-a-methylpyrazinylmalonute.

5. Diethyl a-methyl-S-cyclohexylpyrazinylmalonute.

Table ll-Continued No. Dose (orul) Mg/Kg lnhihition Example Ruts Example Phcnylhutuznnc Example Phcnylbutuzonu X] m I00 100 38 34 X!" 100 mo 41 50 xiv lo I00 I00 27 44 XV m 100 I00 41 6| XVI 10 100 100 56 4x XLlX I0 I00 I00 21 41 10 We clalmz l. A member selected from the group consisting of a compound of the formula:

I5 1 N C-X R I wherein R is a member selected from the group consisting of phenyl, chlorophenyl, dichlorophenyl, fluoro phenyl, trifluoromethylphenyl, lowerulkoxyphenyl,

Page 1 of 2 UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION Q PATENT NO. 3,901,886

DATED August 26, 1975 INVENTOR(S) Schwartz, Norman, et al.

It is certified that error appears in the above-identified patent and that said Letters Patent Q are hereby corrected as shown below:

In Column 1, line t, reads "794386" should read 77 5486 In Column 9, line 26, reads "Steps of" should Q read steps from In Column l t, line 28, reads a-m-ethyl" should read a-methyl In Column 16, line 12, reads "S-cyclohexlpyrazinol" should read 5-cyclohexylpyrazinol In Column 17, line 30, reads "chloropyraine" should read chloropyrazine In Column 17, line 53, reads Example XXIV" should read Example XXXIV In Column 21, line #3, reads omitted entire paragraph prior to Example Table I shows the ultraviolet light absorption characteristics of the compounds identified in the Examples.

Q The solvent employed is methanol Page 2 of 2 UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,901,886

- DATED August 26, 1975 INVENT0R(5) 1 Schwartz, Norman, et al- It is certified that error appears in the above identified patent and that said Letters Patent Q are hereby corrected as shown below:

In Column 21, omitted E to head the third column In Column 22, line 26, move over one column Signed and Scaled this Twenty-ninth D a) of November I 977 [SEAL] Attest:

RUTH C. MASON LUTRELLE F. PARKER Attesting Officer Acting Commissioner of Patents and Trademarks 

1. A MEMBER SELECTED FROM THE GROUP CONSISTING OF A COMPOUND OF THE FORMULA:
 2. Diethyl Alpha -methyl-5-phenylpyrazinylmalonate.
 3. Diethyl Alpha -ethyl-5-phenylpyrazinylmalonate.
 4. Diethyl 5-(p-chlorophenyl)- Alpha -methylpyrazinylmalonate.
 5. Diethyl Alpha -methyl-5-cyclohexylpyrazinylmalonate. 